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The effects of annealing treatment in oxygen ambient on Ni/Al0.09Ga0.91N UV photodetectors

L. S. CHUAH1,* , Z. HASSAN1, H. ABU HASSAN1

Affiliation

  1. Nano-Optoelectronics Research and Technology Laboratory School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia

Abstract

To date, no approaches have been reported on the effects of annealing treatment in oxygen ambient on Ni/Al0.09Ga0.91N metal-semiconductor-metal (MSM) photodiodes. In this work, unintentionally doped n-type Al0.09Ga0.91N samples were grown by radio frequency (RF) nitrogen plasma-assisted molecular beam epitaxy (MBE) on (111) silicon substrates. High temperature grown AlN (about 200 nm) was used as a buffer layer. MSM photodiode was fabricated on the AlGaN samples with a nickel layer as transparent coplanar Schottky contact. The Ni/Al0.09Ga0.91N samples were annealed at a range of temperatures starting from 400 °C to 700 °C in flowing oxygen by using a tube furnace. The effect of post annealing in oxygen ambient on the electrical properties of Ni/AlGaN is studied by current-voltage (I-V) measurement. We have measured Schottky barrier heights (SBHs) and junction ideality factor (n) straight on the MSM photodiodes. It was found that dark current of the detector became significantly smaller after annealing. With a 10 V applied bias, it was found that we can achieve a photocurrent to dark current contrast ratio of 12 from the photodetectors with 600 ºC annealed Ni contacts. The surface roughness of contacts has been monitored by atomic force microscopy (AFM), and scanning electron microscopy (SEM)..

Keywords

Dark current, Metal-semiconductor-metal photodiodes, Si(111); AlGaN, UV photodetector.

Submitted at: Aug. 6, 2008
Accepted at: Jan. 29, 2009

Citation

L. S. CHUAH, Z. HASSAN, H. ABU HASSAN, The effects of annealing treatment in oxygen ambient on Ni/Al0.09Ga0.91N UV photodetectors, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 1, pp. 76-82 (2009)